This invention relates to surgical devices and methods, and more particularly to devices and methods for assuring availability of a retro-sternal space following a sternotomy.
During the years since the first successful "open heart" operation using extracorporeal circulation was performed, the number and complexity of surgical procedures involving the heart which have been developed and are being electively performed have increased remarkably. Congenital and acquired lesion of the heart in patients of all ages are routinely treated surgically in most developed nations throughout the world. In the United States alone, an estimated 200,000 operations on the structures of the heart are performed annually.
The beneficial consequences from heart surgery combined with acceptable morbidity and morality statistics have produced a level of confidence among physicians which allows them to prescribe surgical intervention on multiple occasions for the same patient. Reoperation on the heart is not uncommon; at least five separate heart operations on the same patient are known to have been performed.
The sternum and the underlying heart are normally anatomically separated by a distance which, although varying with the individual, is typically one to two centimeters. In effect, there exists a tunnel between the internal or posterior surface of the sternum and the front or anterior surface of the heart and pericardium, often referred to as "the retro-sternal space." In nearly all cardiac surgical procedures, access to the heart and great vessels is obtained through a median sternotomy whereby the sternum is longitudinally severed with a specially designed saw and the severed sternal edges are spread apart. During an initial sternotomy the existence of the retro-sternal space or tunnel longitudinally underlying the sternum decreases the probability of inadvertent laceration of the heart or great vessels as the saw cuts through the sternum.
While initial sternotomy is considered to carry an extremely low risk as respecting this type of injury, the risk is substantially increased for a subsequent or "re-do" sternotomy. Obliteration of the retro-sternal space following a sternotomy may permit the anterior wall of the heart to bond to the posterior surface of the sternum. Adhesions which form between the sternum and the heart are evenly distributed over the structures of the heart; however, in most cases the wall of the right ventricle and right atrium are adherent to the sternum. If during a re-do sternotomy the sternal saw enters either of these chambers, the occurrence is immediately apparent but nonremediable until the cut edges of the sternum are spread apart to expose the heart. As the sternal edges are spread the rent in the violated heart chamber is enlarged due to the adhesions between the heart and the sternum in the vicinity of the edges of the laceration. It is considered that the entering of a heart chamber during re-do sternotomy creates a life threatening situation.